Coatings used during the repair of damaged motor vehicles generally include several layers of different coating compositions. The initial coating is usually a primer coating resulting from a coating composition formulated as a primer. Once the gross damage to the underlying substrate has been fixed, a primer layer is applied over the repaired surface. The primer layer is then cured to form a primer coating. The primer coating provides adhesion to the substrate, which can be bare metal, plastic, primed plastic, an electrodeposition layer, primer, topcoat, clearcoat or a combination of these coats. The primer composition is applied to the substrate in a relatively thick layer so that the premier coating resulting therefrom can be readily sanded (also known as ‘flattened’) using sand- or glass-paper to obliterate minor imperfections in the substrate and provide a smooth surface for subsequent coatings. The primer commonly contains pigments, fillers, or a combination thereof for ease of sandability. Typically, the thickness of the primer coating ranges from 50 to 200 μm. Over the primer coating, a topcoating is applied which itself can result from more than one type of coating compositions, such as such as basecoat and clearcoat compositions.
U.S. 6,838,177 describes a process for priming a surface using a UV curable primer wherein the ratio of UV-B to UV-A radiation in the radiation source is 1:1 or less. As taught by the examples in the '177 patent, all of the cured coating compositions need to be wiped with a solvent to remove sticky uncured surface layer prior to further processing.
It would be desirable to have a coating composition that can be readily cured by using visible light or UV radiation that has essentially no UV-B radiation into a dry-to-the touch coating after a cure time ranging from 30 seconds to 10 minutes without the need to wipe the surface to remove uncured portions of the coating composition. The inventive coating composition has the aforementioned abilities.